The substitution of A-site alkali ions and B-site transition metal ions of the perovskite oxide oxygen-permeating membrane system of La1-xSrxTi1-yFeyO3-delta (LSTF) has been studied for their application to the partial oxidation of methane to syngas. Both the substitution of Fe for Ti, and the substitution of Sr for La increased the p-type electronic and oxygen ionic conductivities to 155 and 0.47 S cm(-1) respectively. From 800 to 1000 degrees C, the temperature dependence of conductivity has been studied, and the thermal activation energy of the p-type electronic conductivity of La0.6Sr0.4Ti0.1Fe0.9O3-delta was found to be 38 kJ/mol and those of the ionic conductivity of La0.6Sr0.4Ti1-yFeyO3-delta (y=0.7 and 0.9) were 11 and 20 kJ/mol. The thermal expansion coefficients of LSTF were varied from 10.8 to 17.0 (x 10(-6)/K-1) by increasing the Fe substitution. La0.6Sr0.4Ti0.3Fe0.7O3-delta was the optimized composition with a good trade-off of the high ion conductivity, 0.07 S cm(-1), and good matching of the thermal expansion coefficient, 12.4 x 10(-6)/K-1. It has been tested for the partial oxidation of methane to syngas and shows a high oxygen permeation rate of 13.8 cm(3)/min/cm(2) at 1000 degrees C or 10.5 cm(3)/min/cm(2) at 900 degrees C. In addition, High values of CH4 conversion and CO selectivity were confirmed at 900 degrees C, 60.0% and 99.9% respectively. (C) 2010 Elsevier B.V. All rights reserved.